If it was a moon hoax, we all know that Russia, China, East Germany and other cold-war enemies of the USA closely monitored the lunar missions. It was easy to tell whether the Apollo radio signals were coming from the direction of the Moon, and whether the time delays in conversation matched the distance the signals had to travel. If anything had seemed wrong, surely these unfriendly countries would have loudly shouted to the world that the USA was pulling a hoax! Yet none of them ever questioned NASA's accomplishment. When even your enemy gives you credit for something, it's pretty convincing!